14 Benefits of Green Tea + Side Effects & Risks

14 Benefits of Green Tea + Side Effects & Risks

Green tea contains nutrients and antioxidants that provide many health benefits – from reducing the risk of heart disease, cancer, and diabetes to increasing longevity or improving brain function. Read this article to learn all about this nutritional drink. What Is Green Tea?

Green tea is a type of tea made from the same plant as black and oolong tea ( Camellia sinensis ). However, the leaves and buds used to make green tea don’t undergo the same withering and oxidation processes than those employed in these two other tea types.

Green tea contains polyphenols and catechins, which are antioxidant micronutrients naturally found in plants. By reducing free radical production, they may help prevent several diseases.

Epigallocatechin gallate ( EGCG ) is the main polyphenol found in green tea and has many potential benefits to human health [ 1 ].

L- theanine , an amino acid similar to glutamate and glutamine , is another component abundantly found in green tea. It has been specially investigated for its potential to improve cognitive function and curb anxiety [ 2 , 3 ].

Green tea is also a rich source of minerals [ 1 ]. Snapshot

Proponents

High content of antioxidant compounds

Approved for genital and anal warts

May help prevent heart disease

May help prevent some cancer types

May help prevent diabetes

May improve cognitive function

May improve oral health

May help lose weight

Skeptics

Insufficient evidence for some benefits

May cause adverse effects associated with caffeine

High doses may damage the liver

May contain toxic levels of aluminum

Lowered testosterone, reduced iron absorption, damaged the pancreas, and enlarged the thyroid gland in animal studies

Health Benefits of Green Tea

Effective for:

Warts

A topical ointment with green tea extract (Polyphenon E, also called Sinecatechins) was approved by the FDA in 2006 for the treatment of genital and anal warts. In 4 clinical trials on over 2,200 people, it was effective and well-tolerated [ 4 , 5 , 6 , 7 ]. Likely Effective for:

Preventing Heart Disease A meta-analysis of 9 studies and almost 260,000 people associated green tea consumption with a reduced incidence of heart disease. It was dose-dependently associated with fewer heart attacks. Drinking over 10 cups/day was associated with lower LDL levels. Its flavanols were identified as the protective compounds in another meta-analysis [ 8 , 9 ].This protective effect seems largely due to its ability to lower blood pressure and improve blood fat profile. Multiple meta-analyses of clinical trials found that drinking green tea reduced blood pressure, total cholesterol , and LDL cholesterol [ 10 , 11 , 12 , 13 , 14 , 15 ].The evidence suggests that green tea may help prevent heart disease by lowering blood pressure and cholesterol (both total and bound to LDL). You may discuss with your doctor if it may help as a complementary measure in your case. Possibly Effective for: 1) Increasing Longevity In 2 studies of over 350,000 Japanese elderly people, drinking more than 3 cups of green tea per day was associated with lower rates of death from all causes, heart disease, stroke, and respiratory diseases in both genders and from cancer in women [ 16 , 17 ].In another study on over 14,000 Japanese elderly people, drinking green tea was associated with a 76% lower mortality during the 6-year follow-up period of the study. Green tea was associated with reduced death from all causes and heart disease, as well as with a lower incidence of colorectal cancer [ 18 ].Polyphenols in green tea protected telomeres from shortening in cell-based studies, suggesting their potential to increase longevity [ 19 ].All in all, the evidence suggests that green tea may help increase longevity. You may combine it with a healthy lifestyle if your doctor recommends it. 2) Preventing Cancer Oxidative damage may trigger several cancer types. As a rich source of antioxidants, green tea may help prevent them [ 20 ]. Colorectal Cancer In an observational study on almost 70,000 Chinese women, regular consumption of green tea was associated with a reduced incidence of colorectal cancer [ 21 ].Although they generally concluded that the evidence was insufficient and larger, better-designed clinical studies were needed, 4 meta-analyses associated drinking green tea with a lower incidence of colorectal cancer [ 22 , 23 , 24 , 25 ].In 2 clinical trials on 276 people, supplementation with green tea extract reduced the incidence of a colorectal cancer type (metachronous colorectal adenoma) [ 26 , 27 ].In a study on over 4,000 French women, consuming green tea and other antioxidant beverages was associated with a lower incidence of breast cancer. However, a study on over 1,500 women failed to associate regular green tea intake with breast cancer [ 28 , 29 ].In a small clinical trial on 12 women with breast cancer, a formulation with epigallocatechin gallate efficiently delivered this polyphenol into the blood and tumors and reduced a biomarker of breast cancer (Ki-67) [ 30 ].Meta-analyses found a slight trend towards reducing breast cancer incidence in women drinking high amounts of green tea, although they generally considered the evidence insufficient due to the high heterogeneity of the studies. The most recent meta-analysis did find green tea effective at protecting from breast cancer, especially from its recurrence [ 31 , 32 , 33 , 34 , 35 ]. Prostate Cancer In an observational study on almost 50,000 Japanese men, green tea consumption was associated with a reduced frequency of advanced prostate cancer [ 36 ].Two meta-analyses concluded that green but not black tea may help prevent prostate cancer, especially in Asians and in people taking over 7 cups/day. However, another meta-analysis of 21 studies found no association [ 37 , 38 , 39 ].In a clinical trial on 60 men with a condition that often develops into prostate cancer (high-grade prostate intraepithelial neoplasia), the daily treatment with green tea catechins helped prevent this type of cancer. However, a similar trial on almost […]

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